The invention relates to a suction device, in particular for a heart-lung machine, comprising an aspirator, a suction line and a suction pump.
The invention relates furthermore to a method for switching on and off a pump which is used in particular in combination with a heart-lung machine and which suctions up a liquid through an aspirator.
In order to work on and in the heart during heart operations, with the aid of heart-lung machine, the blood of the patient is diverted into the heart-lung machine through tubes, which are inserted into the large veins of the body, and after saturation of the blood with oxygen in an oxygenator, and is led back to the patient with a hose pump or a centrifugal pump through a cannula which opens out into the aorta. By clamping off, or respectively pinching, the large blood vessels close to the heart, the heart is taken out of the blood circulation. The necessary operative procedure can be carried out on a bloodless heart. Although the main portion of the blood runs through the heart-lung machine, blood oozes out of the surgical wounds into the heart and lung cavity as well as out of the pulmonary vascular bed into the heart. In the case of congenital heart defects, up to 40% of the circulating blood can inundate the heart and thus the operation region, so that the surgeon loses sight of the defect to be corrected in and on the heart. During use of the heart-lung machine in an average heart operation of about 90 to 120 minutes, up to 40 liters of blood can accumulate. This blood cannot be returned directly to the circulation, but instead is suctioned up separately through a suction device associated with the heart-lung machine, and after deaeration and microfiltration, is fed back to the circulation in a continuous way. In the case of careful work without any complications, blood loss during heart operations is very minimal. A high percentage of patients need no foreign blood up until their release from the hospital.
In the known suction devices suitable for heart surgery, an aspirator, on whose free end an aspirator tip with suction openings has been disposed, is connected to a suction pump via a suction line. The suction line is designed as a PVS or silicon hose, which can be inserted into a U-shaped pump body of the suction pump constructed as a hose pump. Two opposite rollers are led over the hose at up to 250 revolutions per minute, and thereby suction up the accumulating blood out of the operation region through the aspirator, with its suction tip placed in the operation region, and lead the blood into a blood reservoir (cardiotomy reservoir). During the suction procedure a quantity of air is suctioned up as well. The suctioned up blood-air mixture presents a special problem since damage to the blood corpuscles and to the coagulation system of the blood occur through the arising shear forces and through the direct air contact. Gentle treatment with the aspirators and avoidance of air admixture is an important prerequisite for the well-being of the patient after the operative procedure. Owing to the disposition of the heart-lung machine with respect to the patient, the operator of the machine (cardiotechnician) has no view into the operation region and no eye contact with is the surgeon. Disadvantageous therefore is that the switching on and off or respectively the control of the suction pump must take place on the basis of a shout from the surgeon or respectively on the basis of the suction sound. This situation, above all in critical situations, results in situations of stress for surgeons and cardiotechnicians.
Object of the present invention is therefore to improve a suction device, which is especially suitable for a heart-lung machine, in such a way that the suction pump switches on and off automatically.
The object is achieved according to the invention in that the aspirator has a sensor to detect fluid, which sensor is connected to the suction pump via a signal line.
Through the placement of the sensor in the aspirator it is possible to distinguish liquid from air and to start the suction pump when liquid is present, i.e. when blood is present, and to stop the suction pump automatically upon admission of air. Vortices of air with the blood are thereby minimized, and the suctioning up of blood no longer has to be started by the surgeon by shouting.
According to a preferred embodiment of the invention, the sensor is disposed in the region of a free end, remote from the suction pump, of a suction tip of the aspirator. By disposing the sensor in the region of the aspirator tip, the fluid to be suctioned up can be detected early in the vicinity of the suction openings disposed on the tip.
According to a further preferred embodiment, the sensor is designed as an optical element in which, depending upon the surrounding medium, light can be passed on by total reflection. A sensor unit has a laser diode as the optical transmitter, which is connected to the optical element via a first light guide. The sensor unit has furthermore an optical receiver, which is designed as a photodiode and is connectible to the sensor via a second light guide as part of the signal line. If the optical element is surrounded by liquid, or respectively blood, the light reflected by the laser diode via the first light guide into the optical element will be at least partially decoupled in the liquid. If the optical element is surrounded by air, the light of the laser diode coupled in the optical element is passed on through total reflection in the optical element, and reaches the optical receiver, designed as a photodiode, via the second light guide. By using an optical transmitter in connection with light guides, it is possible to forego an electrically conducting connection between sensor and sensor unit, which is of particular safety-technical significance during use on a patient. By means of this configuration moreover not only a qualitative but also a quantitative control of the suction pump is possible.
According to a further preferred embodiment, the optical element is designed as a light guide fiber piece with the cladding surface as the optical interface. It is thereby possible for first light guide, optical element and second light guide to be formed by a continuous light guide fiber.
According to a further preferred embodiment of the invention, optical transmitter and optical receiver are connected to the optical element through the same optical light guide. Transmitter and receiver are thereby connected via a Y coupler with the front face of the light guide turned toward them. This has the advantage that it is possible to use just one light guide fiber as the light guide, saving space. Moreover it is possible to form the optical elementxe2x80x94for example as a tip of a conexe2x80x94on the light guide""s front face remote from the sensor unit.
Disadvantageous in the known methods for switching a suction pump on and off, used especially in combination with a heart-lung machine, is that the suction pump connected to the aspirator has to be switched on and off by hand.
A further object of the invention, therefore, is to improve a method for switching a suction pump on and off, which is used in particular in combination with a heart-lung machine, in such a way that an automatic switching on and off of the pump is possible.
This object is achieved in that a sensor disposed on the aspirator detects fluid to be suctioned up, and emits a sensor signal for automatic switching on and off of the pump.
Through the detection of the fluid to be suctioned up and through the emission of a sensor signal, an automatic suctioning up, or respectively a automatic switching on and off of the suction pump, is made possible. The suctioning up no longer has to be started by a shout. Through the detection of the fluid, the traumatization of the blood through air impurities is reduced during the suctioning up of blood.
According to a preferred embodiment of the method, a sensor signal is received from sensor electronics of a sensor unit, is evaluated, and is passed on to the suction pump as the control signal. This allows not only a qualitative, but also a quantitative control of the suction device.
According to a further preferred embodiment of the method, a light signal is supplied to the sensor from an optical transmitter, which signal the sensor passes on in air to an optical receiver, and in liquid diverts at least partially into the liquid. The light signal is passed on thereby in a light guide fiber from the optical transmitter to the sensor and from the sensor to the optical receiver by total reflection.
By using an optical sensor with optical signal line, an electrical connection between aspirator and sensor unit can be omitted.
Further particulars of the invention result from the following detailed description and the enclosed drawings, in which preferred embodiments of the invention are illustrated by way of example.